The introduction into motor vehicles of systems for automatic stopping/restarting of the thermal engine, known as stop and go, has made the voltage constraints on the on-board electrical networks of the vehicles more critical.
In general, the power of the rotary electrical machine which ensures the starting of the thermal engine has been increased in order to facilitate the starting of the engine and prevent a certain number of disadvantages which the multiple operations of restarting of the engine could cause for the users. Consequently, there is a higher current spike drawn from the battery during starting of the engine, and correspondingly large voltage drops on the on-board network. This problem of large voltage drops arises in the two architectures known in the stop and go system, i.e. the architecture with an alternator-starter and the architecture with a restarter, also known as reinforced starter.
The integration of a device for maintaining voltage in a system for automatic stopping/restarting of the thermal engine is a possible response to the aforementioned problem. In the system with an alternator-starter, the integration of a device for maintaining voltage also has the advantage of permitting an increase in the torque of the machine, which increase in the torque is derived from the possibility of supplying the excitation circuit of the rotor with a voltage which is far higher than the nominal voltage of 14 V, of the conventional on-board network.
In the prior art, a system created by the inventive body is known, with an alternator-starter equipped with a device for maintaining voltage, which can make the on-board network voltage increase to a value of approximately 17.5 V.
It will be noted however that most of the electronic accessories and equipment which are connected to the on-board network of the vehicle are not designed to withstand repeatedly an on-board network voltage of approximately 17.5 V. In fact, these electronic accessories and equipment have generally been designed for a standard on-board network of 12 V.